The invention relates more particularly to radiotelephone networks of the GSM type, and to those of types derived from the GSM type and which include a stationary satellite, or satellites in low earth orbit (LEO). GSM type networks have the following characteristics:
a geographical zone subdivided into cells so as to enable carrier frequencies to be reused; PA1 a gateway manages the resources of each cell concerning carrier frequencies and the plurality of channels carried by each carrier frequency; and PA1 at least one switching center of the mobile radio service manages: calls, connections with the fixed telephone network, and databases, which databases contain the directory number, the international mobile subscriber number, and the location of each mobile subscriber. PA1 call forwarding means for forwarding a call addressed to one of the user terminals and containing the directory number of the called user terminal to a mobile service switching center providing access to the called user terminal, the forwarded call containing a directory number designating a first fixed radiotelephone terminal associated with the directory number of the called user terminal; and PA1 means situated in said center to act as follows:
Conventional GSM networks or networks derived therefrom are not designed to enable a plurality of subscribers to use the same user terminal. The user personalizes the terminal being used by inserting a subscriber identification module (SIM) card therein containing the international mobile subscriber identity (IMSI) which determines the account to which calls will be billed. After an initialization stage, the terminal is specified in radio messages by a temporary mobile subscriber identity (TMSI) which serves to protect the user's anonymity. In addition, an authentication procedure uses a secret key contained in the SIM card to prevent a user making fraudulent use of the IMSI or the TMSI of another user, whenever a call is made or received.
The use of a plurality of fixed radiotelephone terminals to connect a single switch to a GSM network poses a problem of coordinating the terminals, and also a problem of supplying the switch with the identity of a called line.